In the case of JEB v. Alabama ex rel. T.B. (1994), the Supreme Court ruled that peremptory challenges based on gender are a violation of the Equal Protection Clause of the Fourteenth Amendment. The state of Alabama used peremptory challenges to exclude male jurors from a jury in a child support case.
Of the options you presented, the most accurate response would be:
Peremptory challenges on the basis of gender were a violation of the Sixth Amendment.
However, it's important to note that the actual ruling was more focused on the Equal Protection Clause rather than the Sixth Amendment. The ruling underscored that using peremptory challenges to discriminate against jurors based on gender (similar to race) is unconstitutional.